Share this article

Scientists think exposure to night-time light disrupts the production of melatonin, setting in motion a chain of events inside the body that might encourage tumour development.

The findings come at a time when flexible working patterns are being deployed on a larger scale than ever before in the UK.

According to the Health and Safety Executive, at least 3.6 million people - or around 14 per cent of the working population - regularly work shifts.

In the latest study, published in the American Journal of Epidemiology, researchers studied 3,137 men who had been diagnosed with a range of different types of cancer.

As part of the study, they analysed how many of the men had regularly worked nights and compared the results with working patterns in another group of more than 500 cancer-free men.

The researchers found night shifts almost trebled the risk of prostate cancer and doubled a man’s chances of bowel cancer.

Night workers were also 76 per cent more likely to suffer lung cancer and 70 per cent more at risk of a tumour in the bladder.

For prostate, bowel and bladder cancer, the dangers were greatest among those who had worked nights for at least ten years.

In a report on their findings the researchers said: ‘Several studies have assessed the possible association between night work, particularly among nurses, and breast cancer. But little evidence has been accrued regarding cancer at other sites, or among males.

‘The observation here of elevated risks for several other types of cancer is novel.

‘One thing is certain - if our findings are valid, it would signal an important systemic (affecting the whole body) tumour hazard.’

Nearly 40,000 cases of prostate cancer are diagnosed every year in the UK and 10,000 men die from it - the equivalent of more than one an hour.Bowel cancer, meanwhile, affects around 41,000 people a year, half of them men.